AC electrokinetics is becoming a strategic tool for lab-on-a-chip systems due to its versatility and its high level of integration. The ability to foreseen the behaviour of fluids and particles under nonuniform AC electric fields is important to allow new generations of devices. Though most of studies predicted motion of particles in co-planar electrodes configurations, we explore a pure 3-D AC electrokinetic effect that can open the way to enhance contact-less handling throughout the microchannel. By fabricating 3D microfluidic chips with a bi-layer electrodes configuration where electrodes are patterned on both sides of the microfluidic channel, we present a detailed study of the AC electrokinetic regimes that govern particles motion suspended in different host media subjected to a non-uniform AC electric field that spreads through the cross-section of the microchannel. We simulate and observe the motion of 1, 5, and 10 lm polystyrene particles relative to the electrodes and provide an insight on the competition between electro-hydrodynamical forces and dielectrophoresis. We demonstrate that using relevant electrode designs combined with the appropriate applied AC potential, particles can be handled in 3-D in the micro-channel at a single or a collective level in several medium conductivities. Both numerical simulations and experimental results provide a useful basis for future biological applications.
This work determines the dielectrophoretic response of surface modified polystyrene and silica colloidal particles by experimentally measuring their Clausius-Mossotti factors. Commercial charged particles, fabricated ones coated with fibronectin, and Janus particles that have been grafted with fibronectin on one side only were investigated. We show that the dielectrophoretic response of such particles can be controlled by the modification of the chemistry or the anisotropy of their surface. Moreover, by modelling the polarizabilities of those particles, the dielectric parameters of the particles and the grafted layer of protein can be measured.
>New Method to determine Claussius-Mossotti factor of colloidal particles embedded by Embedded Video
Article: 2011 Determination of Clausius-Mossotti factors and surface capacitances
Flip-Flops of 1 µm PS / 100 nm Au JPs were performed by time triggering the switching frequency between flip and flop. Perfomance rotations were up to 20 Hz.embedded by Embedded Video
Janus particles are particles that are different on each side on a chemical of physical point of view.
We have created 1 µm PS/100nm AU JPs and trapped them with DEP in 3D. We have shown that rotation around their axis can be controlled by changing the applied potential frequency or voltage.embedded by Embedded Video
Shifted vertical electrodes were put each other one at AC potential to create negative DEP, f= 2MHz and Vp-p=20Vembedded by Embedded Video
Using dielectrophoresis to repeal particles from squared like electrodes on the top and bottom of the microfluidic channel. PS 1µm, f=2MHz and Vp-p=20 Vembedded by Embedded Video
Using dielectrophoresis, particles of polystyrene 1 µm were focalized with an AC potential applied on 4 funnel shaped ITO electrodes. f=2MHz and Vp-p=20Vembedded by Embedded Video